^^^^
All the screws.....Why would you do only one?

Decent set of lightguards with security screws and as mentioned I too have resined ballbearings into the door hinge torx screw heads.

There are numerous relatively cheap and quick methods to achieve the 'layered approach.' Not a cure but if it holds them up a while they may lose interest. From another thread.....

K9F wrote:

This is from another website and I think the 'ethos' behind the 'layered approach' is possibly the best way and is the one I myself have adopted, needn't cost a packet either..for example applying resin/ball bearings to torx screws etc....



It is clear that there is no single magic solution to security. Each security product just buys you time - and it is time that is the real deterrent to potential thieves, not loud alarms nor flashing lights. Most people simply ignore alarms. The more time your vehicle takes to steal, the greater the chance a potential thief will be caught so the more likely they are to move on to a less protected vehicle.

Curiously, the magic time delay is roughly 2 minutes. A delay of 2 mins will make most thieves move to another vehicle. A delay of 4 mins will not give you twice the protection (a case of diminishing returns). However, two security products which each take more than 2 minutes to defeat does seem to offer double the protection. This is the reason specialists recommend a 'layered' approach. Each product provides one layer of protection and you decide how many layers you need for the risk in your area.